1. Field of the Invention
The present invention relates to devices for crawling through pipes. More particularly, the present invention relates to a pipe crawler having a midsection that provides both the stability and the flexibility necessary to efficiently negotiate bends in piping systems.
2. Discussion of Background
Many vehicles are known for moving through piping systems, including vehicles that carry inspection equipment and vehicles push or pull inspection equipment carried by a separate vehicle. Vehicles that are self-propelled are sometimes called pipe crawlers. The inspection equipment is used to assist in determining the structural integrity of piping that is otherwise difficult or impossible to inspect from the outside, such as underground piping or piping in hazardous or less than desirable locations. Due to the difficulty of moving through non-linear or uneven segments of piping, numerous pipe crawlers and associated equipment have been developed. See for example, U.S. Pat. Nos. 5,121,694 and 5,018,451.
Pipe crawlers are usually comprised of a front leg assembly, a rear leg assembly and, optionally, at least one intermediate body therebetween for moving one leg assembly with respect to the other in "inch worm" fashion. In these pipe crawlers, the intermediate body is configured with means for increasing and decreasing the distance between the front and rear leg assemblies so that, when the legs of one assembly are holding the crawler in engagement with the interior surface of the pipe, the legs of the other assembly can be retracted and moved forward. Then the legs of the second assembly hold the crawler while the first assembly moves forward. This series of motions is repeated so that the pipe crawler progresses through the piping.
Pipe crawlers exist that have a single intermediate body or midsection for connecting front and rear assemblies. For example, see U.S. Pat. No. 4,460,920, issued to Weber et al, U.S. Pat. No. 5,142,989, issued to Suzumori et al and U.S. Pat. No. 5,195,392, issued to Moore et al. In U.S. Pat. No. 5,172,639, Wiesman et al disclose a pipe traveler using a series of center bodies to connect a pair of carriages. Also, see co-pending application Ser. No. 08/064,880, now U.S. Pat. No. 5,309,844, commonly assigned, which features a pipe crawler combining a flexible joint and spring suspension system for connecting front and rear assemblies.
In U.S. Pat. No. 4,369,713, Richardson discloses a pipeline crawler with a power unit, a drive unit and a service or inspection unit connected by universal joints. The intermediate drive unit has wheel means that fold outwardly to engage the pipeline.
In U.S. Pat. No. 4,131,018, Muller et al describe a manipulator assembly for pipe testing that has a first vehicular member, a test system carrier member and a midsection positioned therebetween. The midsection has universal joints at each end for connecting each vehicular member to each other or to the test system carrier member. The midsection also has radially extending and retractable support legs with wheels.
Although numerous pipe crawlers exist, there is a need for a pipe crawler that has sufficient flexibility for negotiating curved and uneven portions of piping and yet provides the stability necessary to maintain the proper spatial positioning of the pipe crawler within the piping.